The present invention relates to a centrifugal blood pump, especially for a heart substitute device.
A centrifugal blood pump is known comprising a housing having at least one blood outlet and at least one blood inlet which is closed in a liquid and gas-tight manner except at the blood outlets and inlets and a rotatable pump rotor arranged in the housing, which is driven by an external drive motor located outside of the housing by means of a magnetic coupling.
Centrifugal blood pumps are becoming more important than the so-called roller pumps and also the ventricular pumps for feeding blood, since the disadvantages of these latter blood pumps can be avoided with them. With the easy-to-operate and economical roller pumps these disadvantages include an insensitivity to the medium being pumped, since roller pumps are pure displacement pumps so that, when a connected blood reservoir is empty, air could be pumped into a patient from it with fatal consequences. Furthermore an arbitrarily higher pressure can build up in the system if the blood flow is blocked. Because of the continuous pressing action of the roller on a blood feed tube mechanical hemolysis is unavoidable and an embolytic danger of significant abrasion in the inside of the tube results.
The main disadvantage to the ventrical pump, besides the possible feeding of air, is that its construction is difficult because of its membranes and valves so that it is correspondingly expensive and thus is not suitable for a one-way device required by safety considerations.
In contrast the centrifugal blood pump has the advantage that pumping action is immediately interrupted during a large air inflow. Also mechanical abrasion of plastic particles and their spreading into the blood stream need not be taken into consideration. Blood damage by rotary pumps is noticeably less than by roller pumps. The centrifugal pumps known up to now used for feeding blood in extracorporeal circulation have however always had the disadvantage that they are expensive to construction, also pump parts used in their construction are articles which can be used only once. Bearings are provided for the rotor outside of the blood conducting regions of the pump, which must be sealed by shaft packing from the blood conducting regions. Additional disadvantages include a disadvantageous loss by frictional heat dissipation, which can lead to a local overheating of blood with a danger of denaturation of blood cell proteins and cell destruction during longer dwell times of blood in the pump. Of course seal-less centrifugal blood pumps and with bearing-less rotors with exclusively magnetic stabilization have already been proposed. These pumps still have the disadvantage of a comparatively large construction expense and expensive control means with electromagnetic feedback based on stability considerations and thus an undesirably large pump rotor, which leads again to a large blood chamber volume with correspondingly larger frictional contact surfaces for the blood and a comparatively longer dwell time of the blood in the pump regions.